STABILITY OF IDEAL THYRISTOR AND DIODE SWITCHING-CIRCUITS

This paper analyzes the stability of a general RLC circuit-with ideal thyristors or diodes and periodic sources. Applications include high p ower thyristor controlled reactor and bridge rectifier circuits. The p eriodic steady states of the circuit are analyzed using a Poincare map and transversality conditions are given to guarantee the smoothness o f the Poincare map, A simple and exact formula for the Jacobian of the Poincare map is proved. Account is taken of the varying state space d imension as diodes switch on and off. When the transversality conditio ns fail, switching times can jump or bifurcate. Examples show that the se switching time bifurcations can cause instability of thyristor circ uits and mode changes of diode circuits. The simplification of the Jac obian formula is used to explain why the switching time bifurcations o ccur and are not predicted by the eigenvalues of the Jacobian. Periodi c orbits of ideal diode circuits are proved to be stable using Jacobia n and incremental energy methods. A source of damping in switching cir cuits is identified.